In Part Three of our multi-episode series on Toilets, we talk to environmental engineer Brian Wheeler about what happens to the things we flush, how waste water is treated, whether a septic tank could realistically double as a crawl space, how our public sanitation systems would defend against a terrorist attack on the water supply, and whether Ben’s story about a friend who upper-decked a Walmart holds water. Be sure to listen to all three episodes so the plot twists don’t confuse you.